1. Field of the Invention
The present invention concerns an arrangement for mounting a parallel-guiding device in a force measuring apparatus, particularly in a balance. A load receiver formed by a first leg of the parallelogram in the parallel-guiding device and serving to receive the load to be measured is guided in parallel motion relative to a second leg of the parallelogram by two mutually parallel guide links that are rigid in their lengthwise direction but elastically flexible to bend in the plane of the parallelogram. The second leg of the parallelogram has a fastening area serving to mount it on a supporting part of the force-measuring apparatus, and it also has a portion that projects into the space inside the parallel-guiding device that is delimited by the two guide links. In the direction transverse to the plane of the parallelogram, the parallel-guiding device is delimited by two lateral boundary surfaces that are parallel to the plane of the parallelogram, with the legs of the parallelogram and the guide links extending between them.
2. Description of the Related Art
In mounting arrangements of this kind, the fastening area of the stationary second leg of the parallelogram has to take up the entire moment generated by the force that is to be measured and that acts on the first leg of the parallelogram. This can cause deformations of the parallel-guiding device. In addition, the mounting attachment of the second leg of the parallelogram at its fastening area can introduce stresses into the parallel-guiding device and into parts connected to it. The deformations as well as the mounting stresses can be detrimental to the measuring accuracy.
In a known arrangement of the kind named at the beginning (DE 43 05 425 A1), the stationary as well as the movable leg of the parallelogram have the shape of a hollow profile whose cross-section in the plane of the parallelogram is triangular. The respective sides of the triangle of the stationary and of the movable leg of the parallelogram that extend in the lengthwise direction of the guide links toward the outside of the parallel-guiding device serve as mounting surface to a base plate of the balance and as fastening support for a weighing pan, respectively. Through this sturdy design of the two legs of the parallelogram in the shape of hollow profiles and through the associated mounting geometry, it is possible, admittedly, to alleviate the problems of stress introduction and deformation. However, this design configuration is space-consuming and requires a relatively large amount of material.
Also known (EP 0 573 806 A1) is a design where, in order to reduce unwanted stresses, the block-shaped measuring cell of a force-measuring apparatus is arranged between the two legs of a stiff U-profile that extend parallel to the main planes of the block. By one of its lateral surfaces extending between the main planes of the block, the measuring cell is attached to the bottom portion of the U that connects the two legs. But here, too, the U-profile represents a relatively expensive component. Also, exacting requirements need to be imposed on the lateral surface of the measuring cell that serves for the mounting attachment and on the inside of the U-profile that is in contact with it.